The contents of the directory must match the contents of a corresponding
Java EE archive file. For example, if you deploy a Web application
from a directory, the contents of the directory must be the same as
a corresponding WAR file. In addition, the directories holding the
individual modules must be named with _jar, _war and _rar suffixes. For information about
the required directory contents, see the appropriate specifications.

You can change the deployment descriptor files directly in the
exploded directory. If your environment is configured to use dynamic
reloading, you can also dynamically reload applications deployed from
the directory. For more information, see Dynamic Reloading.

Note –

On Windows, if you are deploying a directory on a mapped
drive, you must be running the Application Server as the same user to which
the mapped drive is assigned, or the Application Server won’t see
the directory.